What do placards on a tanker bearing hazardous materials show?

They show a series of recognizable codes for dealing with the chemical being transported - in case of emergency. This includes... A symbol showing the type of chemical (toxic, flammable etc) - a code to tell emergency services what to do in the event of a spillage - a unique code representing the actual chemical being transported - and an emergency contact number to an information center which will give detailed advice on how to deal with the chemical.